An OEL device, which is a component of an OEL display, generally has an OEL element and a thin film transistor (TFT) for driving the OEL element. A general OEL device has a driving transistor (driving TFT) for driving the OEL element and a switching transistor (switching TFT) for turning on/off the driving transistor.
As an example of typical structure of the OEL device, a top-emission structure in which an OEL element is laminated on a transistor is known (See Patent Document 1, for example). Such an OEL device is called a top-emission type OEL device and emits light from a light emitting layer through a seal film set at the opposite side to a substrate.
FIG. 1 shows a structure of a conventional top-emission type OEL device described in Patent Document 1. In the top-emission type OEL device shown in FIG. 1, a source region 141a of a thin film transistor 123 (driving TFT) for driving is connected to a pixel electrode 111 through a contact hole 145. A drain region 141b of the thin film transistor 123 is connected to a thin film transistor (switching TFT) 142 for switching through a power line 103 provided at a contact hole 146.
In FIG. 1, the thin film transistor 142 for switching connected to the thin film transistor 123 for driving is not shown.
Patent Document 1: Japanese Patent Laid-open Publication No. 2003-249375